Vertebral disc herniation is a common disorder where a portion of a vertebral disc, a cushion-like structure located between the vertebral bodies of the spine, bulges out or extrudes beyond the usual margins of the disc and the spine. Disc herniation is believed to be the result of a excessive loading on the disc in combination with weakening of the annulus due to such factors as aging and genetics. Disc herniation and other degenerative disc disease are also associated with spinal stenosis, a narrowing of the bony and ligamentous structures of the spine. Although disc herniation can occur anywhere along the perimeter of the disc, it occurs more frequently in the posterior and posterior-lateral regions of the disc, where the spinal cord and spinal nerve roots reside. Compression of these neural structures can lead to pain, parasthesias, weakness, urine and fecal incontinence and other neurological symptoms that can substantially impact basic daily activities and quality of life.
Temporary relief of the pain associated with disc herniation is often sought through conservative therapy, which includes positional therapy (e.g. sitting or bending forward to reduce pressure on spine), physical therapy, and drug therapy to reduce pain and inflammation. When conservative therapy fails to resolve a patient's symptoms, surgery may be considered to treat the structural source of the symptoms. Surgical treatments for disc herniation traditionally involve open procedures that require extensive dissection of muscle, connective tissue and bone along a patient's back as well as nerve manipulations to achieve adequate surgical exposure. These surgeries also expose the patient to a significant risk of complications, due to the presence of critical neurovascular structures near the surgical site as well as prolonged anesthesia. For example, a discectomy procedure may be used to decompress the herniation by accessing the affected disc and removing a portion of the disc and any loose disc fragments. To achieve sufficient access to the affected disc, a portion of the lamina or bony arch of the vertebrae may be removed, thereby increasing the invasiveness of the procedure and can destabilize the spine post-surgery. When discectomy fails to resolve a patient's symptoms, more drastic measures may include disc replacement surgery or vertebral fusion.
Fractures of the vertebrae bodies are another common disorder of the spinal column. When a vertebra fractures, the usual shape of the bone becomes compressed and distorted, which results in pain. These vertebral compression fractures (VCF), which may involve the collapse of one or more vertebrae in the spine, are a common finding and result of osteoporosis. Osteoporosis is a disorder that often becomes more severe with age and results in a loss of normal bone density, mass and strength. Osteoporosis often leads to a condition in which bones are increasingly porous or full of small holes and vulnerable to breaking. In addition to osteoporosis, vertebrae can also become weakened by cancer or infection.
In some instances, fractures of the vertebral bodies may be treated with surgical removal of the vertebral body and the implantation of a vertebral body replacement device. Other treatments may include vertebroplasty and kyphoplasty, which are minimally invasive procedures for treating vertebral compression fractures (VCF). In vertebroplasty, physicians use image guidance to inject a cement mixture through a hollow needle into the fractured bone. In kyphoplasty, a balloon is first inserted through the needle into the fractured vertebral body to restore at least some of the height and shape of the vertebral body, followed by removal of the balloon cement injection into the cavity formed by the balloon.